多TDICCD拼接相机成像非均匀性实时校正的硬件实现

摘要

A real-time imaing nonuniformity correction algorithm on a Field Programming Gate Array (FPGA) platform was proposed to modify the imaging nonuniformity of a multi Time Delay Intration (TDI)CCD mosaic camera. Firstly, the definition of Photo Response Nonuniformity(PRNU) and its generation in the multi-TDICCD mosaic camera were introduced. Then, the synthetical correction algorithm was presented,in which the two-point correction method was used in a single channel, gain averaging correction method among multi-channels and the scene-adaptive correction method among multi-TDICCDs. By considering the reliability and the influence of finite word-length of the FPGA, the synthetical correction algorithm was optimized and implemented on the signal processing FPGA platform. Furthermore, a scheme for modifying correction factors and spaceborne calibration were given. The experimental results indicate that the imaging nonuniformity can be decreased from 4. 82% to 0. 27% for a single TDICCD, and to 0. 41% for a 3-TDICCD mosaic camera with the proposed correction algorithm. It also proves that this correction algorithm has high real time performance, good practicality and efficiency, and satisfies the requirements of target projects.%提出了一种基于现场可编程门阵列(FPGA)平台实现的成像非均匀性实时校正算法来解决遥感多时间延迟积分(TDI) CCD拼接相机存在的问题.首先介绍了拼接相机成像非均匀性(PRNU)的定义及其产生的原因,然后针对拼接相机的特点,提出了一种通道内用两点定标法、通道间用增益平均法、片间用自适应场景补偿法的复合非均匀性校正算法.从可靠性和实时性考虑,选择在相机信号处理FPGA硬件平台上实现校正算法,针对FPGA的运算能力改进算法并分析误差,同时给出星上定标和校正因子修正的方案.实验结果表明,该算法可将单片TDICCD的成像非均匀性从4.82％降低到0.27％,最终拼接图像的非均匀性降低到0.41％,且实时性好、效率高、可满足实际工程需求.